Procedure for preparing fish oils



Patented July 14, 1942 2,289,180 I PROCEDURE FOR PREPARING FISH OILSKenneth G. D. Hickman, Rochester, N. Y asslgnor to DistillationProducts, Inc.,

Rochester,

N. Y., a corporation of Delaware No Drawing. Application October 11,1939, Serial No. 298,968

Claims. (Cl. 280-4121) This invention pertains to the art of preparingfish oils and particularly fish body and liver oils of high vitamincontent.

In the fish oil industry it has been found difiicult to prepare oils ofhigh quality as regards odor, taste, color and vitamin content. Thedifficulties which lead to oils of poor quality are encountered not onlyin the processing stage but also during the stages between the time thefish is caught and the time that the fish or its appropriate organs aretreated in the extraction mill. Fish carcasses and organs, such as liverand entrails rapidly decompose. This is particularly true when thefishing is done in warm weather for extended periods of time withoutremoval of the fish catch. As a consequence, the character of the oilsexpressed from fish tissue has been far from satisfactory.

This invention has for its object to provide a process for preventingdestruction and loss of vitamin containing fish oils during the periodbetween the time that the fish'is caught, to and including the time thatthe oil is removed therefrom. A further object is to provide an improvedprocedure for removing oils from fish tissue. Another object is toprovide a procedure for preventing decomposition and rancidification offish tissue and the oils contained therein during the period before theoil is expressed therefrom and/or during the period that the fish tissueis processed to remove its contained oil or any part thereof. Otherobjects will become apparent from the following description.

These and other objects are accomplished by my invention which includesmaintaining the fish tissue and/or its contained oil in intimate contactwith an active oxygen absorber during at least part of the time betweenthe moment that the fish is caught and the time at which the expressedoil is removed from the expressing plant or mill.

In the following description. and claims I have set forth several of thepreferred embodiments of my invention but it is to be understood thatthey are given for the purpose of illustration and,

not in limitation thereof.

In accordance with my invention, the fish tissue which is to be treatedto removeoil therefrom is maintained in contact with substances whichactively absorb oxygen.

By such oxygen absorbers is meant materials which in the solid state orin solution, remove omen, providing a substantially oxygen-freesolution. They are not to be confused with antioxidants which causelittle alteration of the oxygen concentration but serve to preventreaction with this oxygen. One and the same substance may act as anoxygenabsorber and as an antioxidant, and I include within thisinvention substances of both classes whether mixed together or a singlesubstance serving both functions, provided only that one of thefunctions shall be that of active oxygen absorber. Such substances arethe reduced compounds of certain metals and non-metals includingparticularly all the compounds of sulphur and phosphorous capable ofreacting with oxygen or its equivalent, examples are sulfltes andbisulfites such as sodium and potassium sulfltes, hydrosulfites,sulfurous acid, phosphites, hypophosphites, hydrazine, hydroxyl amine,ferrous, titanous, cerous manganous, chlorides, nitrates, sulfatesandother salts of reduced valency. Organic reducing agents such aspyrogallic acid, hydroquincne, diphenyl amine, amidol, etc., may be usedin combination with the active absorbing agents. Substances which formactive oxygen absorbers may be employed.

The fish tissue such as fish carcasses or fish organs may be directlysalted down in the hold in the ship with the active oxygen absorbers.Water tight tanks or barrels would, of course, be preferred but suchequipment is customary. The use of aqueous solutions of the activeoxygen absorbing agents may be desirable, particularly if there isinsuflicient water present in the fish tissue to result in thoroughsolution of the protectm8 substance.

In processing fish body, liver or other tissue to remove oil therefrom,it is customary to employ one of three general types of procedures,namely;

pressing, solvent extraction, or digestion with chemicals such asalkali. Combinations of these procedures are oiten used. Each suchprocedure usually involves as a first step pulping or comminuting thefish tissue in order to increase the surface area present for oilremoval. If the fish tissue. being introduced into the oil removal planthas already been protected in accordance with my invention, it may beunnecessary to add additional oxygen absorbers, or small additionalamounts may be added. However, if untreated fish tissue is to beprocessed, it is desirable to add the absorbing chemical immediately andpreferably before the fish tissue is subjected to the comminutiontreatment. The active oxygen absorbers are then present during theentire processing procedure and exert their protective influencesthroughout. The protective agents can, of course, be added at any stageof the process and as explained above, solids or aqueous solutions ofthe protective agents may be used.

The oxygen absorber can be present during the entire period between thecatchingof the fish to and including the oil removal stages or any partthereof. It is preferred to have these protective agents present duringthe oil processing treatment because during this period the fish tissueis heated, stirred, splashed or flowed in such a manner that it comesinto contact with large volumes of air generally under alkalineconditions which favor reactions with oxygen. The conditions, therefore,are such as to cause extensixe oxidation of the fish tissue, the fishoil and/or the vitamins contained therein. The presence of active oxygenabsorbers in accordance with my invention almost completely avoids lossdue to oxidation at this stage and as a result yields a fish oil of highvitamin content having superior odor, taste, etc., which commands a muchhigher market price.

In some cases, the fish meal after removal of the oil is used forpurposes in which the presence of the sulfites, sulfurous acids, etc.would be undesirable. In such cases volatile sulfites such as ammoniumsulfite or organic sulfites can be used. These can be volatilized fromthe fish residue with little difficulty.

The rate of removal of oil from fish tissue is in some cases dependentupon the hydrogen ion concentration. The use of alkali to raise thehydrogen ion concentration does not in any way harm the beneficialoxygen absorbing agents. This can also be controlled by usingbisulfites, or buffered solutions of sulfite-bisulfite mixtures may beemployed for this purpose.

Example 1 Lingcod when withdrawn from the net are degutted and thelivers removed. The livers and the viscera are separately throwninto'tanks containing a solution of sodium sulfite in strength varyingfrom 1% to a saturated solution. It is arranged that when the vessel isfilled with fish products the mass shall be substantially permeated orcovered by the sodium sulfite solution.

- Alternatively, the livers or viscera may be salted down with solidsodium sulfite and the full vessel may have a substantial layer of solidsodium sulfite thrown on the top before closure. It is intended thatfish products so packed shall be transported and kept in this conditionuntil the time of rendering the oil. They may be frozen in additionduring the period.

At the time of rendering, the livers are unfrozen and thoroughlypulverized. The resulting slurry is tested for the presence of sodiumsulfite, and if the latter has oxidized to a substantial degree, more isadded to keep the solution sufficiently free from oxygen to enable theextraction of the oil to be performed under good conditions. It isgenerally necesary to have present at the beginning of the renderingoperation sodium sulfite in the proportion of 1-10% of the weight of theoriginal livers or viscera.

After the livers have been reduced to a slurry with the sodium sulfite,alkali may be added, and if necessary a quantity of hydroquinone orpyrogallol equal to {6% of the weight of the livers is thrown in. Afterdigestion at temperatures between the prevailing room temperature andthe boiling point of the solution, the mixture is left to settle or iscentrifuged to remove oil. In the case of livers poor in oil, such forinstance as skipjack livers, containing less than of oil, it may bedesirable to add to the slurry with agitation a quantity of low potencyfish oil or a vegetable oil or a low vapor pressure 011, such as a stillresidue oil from the molecular distillation of vegetable or animal oils,the volatile constituents of which have been removed therefrom by thedistillation treatment. In any case, the slurry is passed through thecentrifuge where most of the native oil or oil mixture is'separated. Thewatery portion is returned to another treatment tank where more of thelow potency oil is added and stirred with the centrifuged slurry. Themixture may be tested for sulfite content, and when necessary moresulfite is added with or without organic reducing agent, such ashydroquinone or pyrogallic acid. The mixture is now recirculated throughthe centrifuge, and a quantity of second run fish oil is secured. Thepartially exhausted slurry is returned to extraction tanks as often asnecessary and extracted with further quantities of lowgrade oil with orwithout additional protection with sodium sulfite.

Because of the high electrolyte content of the sulfite slurry, certainwater-soluble materials which would otherwise remain in the aqueousphase may pass into the oily layer. It may be desirable, therefore, towash the oil in plain water or in water containing a lesser quantity ofsulfite or equivalent and again to centrifuge. ess may be repeated asdesired.

Example 2 Salmon-body oil may be secured according to my invention inthe following manner: The salmon having been caught for edible purposes.it is impractical to effect preservation with sodium sulfite. Therejected bodies with or without additional viscera from other bodies arereduced to a slurry in the presence of a 2% solution of sodiumhypophosphite. Alternatively, a 10% solution of sodium sulfite may beused or a 10% solution of a mixture of sodium sulfite and sodiumbisulfite with or without the addition of sodium hydrosulfite. Theslurry after appropriate digestion is centrifuged as in the previousexample to obtain a superior quality of salmon oil. Owing to the lowvitamin content of this oil, it is considered unnecessary to wash theslurry with a further quantity of low-grade or non-vitamin-bearing oil,though this may be done if necessary, as described in the previousexample.

In many cases, it is customary to separate the oil expressed atdifferent stages into separate grades, the oil separated in the laterstages being of poor quality. The second and third grade oils heretoforeprepared have been suitable only as animal feeds and have been of suchlow quality that in many cases they are even unsuitable for treatment toconcentrate their vitamin content by procedure such as high vacuumdistillation or saponification. My procedureresults in oils of goodquality even in the last extraction stages. The oils thus prepared areexcellently suited for treatment by vacuum distillation to separate andconcentrate the Vitamin content thereof. My invention has been found tohave other surprising advantages. The presence of the active oxygenabsorbing agents results in increased 011 yield. In one commercial runthe amount of oil extracted from fish liver was increased 12%. Anothersurprising advantage is that the centrifugal separation of the oil fromthe fish tissue is completed in less time than heretofore required.

The proc- What I claim is:

1.- The process for preparing improved fish oils which comprises addingan active oxygen absorbing material to the fresh or undecomposed fishtissue at some period between the time the fish is caught to andincluding the time the fish tissue is treated to remove oils therefrom,the quantity of active oxygen-absorbing agent which is added beingsuflicient to remove substantially all oxygen and like destructivesubstances present and to maintain the fish tissue in a deoxygenatedcondition whereby the oil and vitamin content of the fish tissue aresubstantially completely protected against deterioration caused byoxygen of the air.

2. In the process for preparing fish oils the improvement whichcomprises adding an active oxygen absorbing agent to fresh orundecomposed fish tissue, from which the oil is to be removed, soonafter the fish tissue is removed from its natural habitat, the quantityof active oxygen-absorbing agent which is added being sufficient toremove substantially all oxygen and like destructive substances presentand to maintain the fish tissue in a deoxygenated condition whereby theoil and vitamin content of the fish tissue are substantially completelyprotected against deterioration caused by oxygen of the air.

3. In the process of preparing fish oil from fresh or undecomposed fishtissue the improvement which comprises maintaining the fish tissue incontact with an active oxygen absorbing agent during at leasta part ofthe processing or extraction treatment, the quantity of activeoxygen-absorbing agent being sufiicient to remove substantially alloxygen and like destructive substances present and to maintain the fishtissue in a deoxygenated condition whereby the oil and vitamin contentof the fish tissue are substantially completely protected againstdeterioration caused by oxygen of the air.

4. In the process of treating fresh or undecomposed fish liver to removefish liver oil therefrom, the step which comprises adding to the fishliver, at some stage of the processing treatment, a substance whichactively absorbs oxygen, the quantity of active oxygen-absorbing agentwhich is added being sufiicient to remove substantially all oxygen andlike destructive substances present and to maintain the fish tissue in adeoxygenated condition whereby the oil and vitamin content of the fishtissue are substantially completely protected against deteriorationcaused by oxygen of the air.

5. In the process of treating fresh or undecomposed fish liver to removefish liver oil therefrom, the step which comprises adding to the fishliver at some stageof the processing treatment a buffered active oxygenabsorbing agent, the quantity of active oxygen-absorbing agent which isadded being sufilcient to remove sub- ..stantially all oxygen and likedestructive substances present and to maintain the fish tissue in adeoxygenated condition whereby the oil and vitamin content of the fishtissue are substantially completely protected against deteriorationcaused by oxygen of the air.

6. The process of claim 5 in which bufiered sodium sulfite is used.

7. In the process of treating fresh or undecom-' posed fish liver toremove oil therefrom, the step which comprises adding sodium sulfite tothe fish liver at some stage during the processing treatment, thequantity of sodium sulfite which is added being sufi'icient to removesubstantially all oxygen and like destructive substances present and tomaintain the fish tissue in a deoxygenated condition whereby the oil andvitamin content of the fish tissue are substantially completelyprotected against deterioration caused by oxygen of the air.

8. The process of protecting fish oils and associated oxidizablesubstances such as vitamins contained in fresh or undecomposed fishtissue against oxidation prior to, and during extraction thereof whichcomprises intimately associating the fish tissue with an active oxygenabsorber such as sodium'sulfite', the quantity of sodium sulfiteassociated with the fish tissue being sufficient to remove substantiallyall oxygen and like destructive substances present and to maintain thefish tissue in a deoxygenated condition whereby the oil and vitamincontent of the fish tissue are substantially completely protectedagainst deterioration caused by oxygen of the air.

9. In the process for preparing fish oils the improvement whichcomprises adding an active oxygen absorbing agent and an antioxidant tothe fresh or undecomposed fish tissue, from which the oil is to beremoved, soon after the fish tissue is removed from its natural habitat,the quantity of active oxygen-absorbing agent which is added beingsufiicient to remove substantially all oxygen and like destructivesubstances prescut and to maintain the fish tissue in a. deoxygenatedcondition whereby the oil and vitamin content of the fish tissue aresubstantially completely protected against deterioration caused byoxygen of the air.

10. In the process for preparing vitamin-containing fish oils byextraction of fresh or undecomposed fish tissue the step which comprisesextracting the oil from the fish tissue while the fish tissue ismaintained in the presence of a sufficient amount of activeoxygen-absorbing agent to remove substantially all oxygen and likedestructive substances present and to maintain the fish tissue in adeoxygenated condition whereby the oil and vitamin content of the fishtissue are substantially completely protected against deteriorationcaused by oxygen of the air.

KENNETH C. D. HICKMAN.

